Site-selective and Stark spectroscopy of the series [Os(2,2′- bipyridine)3-x(2,2′-bipyridine-d8)x] 2+ (x=0-3) in single-crystal [Ru(2,2′-bipyridine) 3](PF6)2. Localization of an intramolecular triplet metal-to-ligand charge transfer exciton by partial deuteration

Abstract

Selective luminescence and excitation spectroscopy and Stark experiments of the title systems are reported. Dramatic differences of the x=1 and x=2 spectra, in comparison with the x=0 and x=3 spectra are observed. The lowest-excited state in the x=1 and x=2 spectra is a charge-transfer excitation localized on the protonated ligand(s). A superposition of "deuterated" and "protonated" transitions is observed for the x=1 and x=2 systems in the excitation spectra. The deuteration shift (≈32 cm-1) is much larger than the excitation exchange interaction β between the metal-ligand subunits. |β| is ≈2 cm-1, as directly determined from the observed splittings (5-7 cm-1) of I, the lowest-energy electronic origin. Stark shifts confirm the charge transfer character of the lowest-excited states. The splittings and relative intensities of the origins and their Stark effect can be quantitatively described by an exciton formalism. Show more